A nickname that is typically used by blacks to refer to any white male.
This modern usage of "Opie" is most likely derived from the character Opie Taylor (played by Ron Howard) on "The Andy Griffith Show" who was the hick son of a hick sherriff in a hick town called Mayberry.
Others characters on this show have also spawned modern nicknames (See Gomer Pyle, Goober Pyle, Aunt Bea, Barney Fife).